WO2001028284A1

WO2001028284A1 - Sound-collecting device

Info

Publication number: WO2001028284A1
Application number: PCT/JP2000/007169
Authority: WO
Inventors: Alexander Kots; Okihiro Kobayashi; Nobuhiro Miyahara
Original assignee: Phone-Or Ltd.; Paritsky, Alexander
Priority date: 1999-10-15
Filing date: 2000-10-16
Publication date: 2001-04-19
Also published as: EP1150541A1; JP2001119785A; US20020080982A1; US6459798B1

Abstract

A device for collecting sounds from objects comprises a plurality of microphones whose directivity can be varied depending on the environment in which each object is located. An optical microphone includes a vibration board (2) which vibrates by sound pressure, a light source (3) for emitting a light beam to the vibration board (2), a photodetector (5) which receives the light beam reflected from the vibration board (2) and produces a signal corresponding to the vibration of the vibration board (2), a drive circuit (13) for supplying the light source (3) with predetermined current, and a negative feedback circuit (100) that supplies the drive circuit (13) with a negative feedback signal consisting of a signal output from the photodetector (5). The negative feedback circuit (100) changes the amount of negative feedback depending on the environment.

Description

Technical field

The present invention relates to a sound collecting device, and more particularly to a sound collecting device capable of setting an optimum microphone characteristic according to a use environment. Background art

Conventionally, there has been known an accessory microphone which is selected so as to have an optimum microphone characteristic according to the purpose of sound collection.

There are various types of such accessory microphones, such as a desktop type, built-in type, nose type, and hand type, depending on the application. Functionally, omnidirectional type and single directional type are available. Are known.

Also known is a microphone that can be switched between a standard microphone and a telephoto microphone according to the type of operation. Depending on the shape of the microphone, microphones classified into vocal type, stand type, and 'clip type' are used.

Thus, various microphones have been used as conventional conventional microphones according to their functions and applications.

However, none of the conventional accessory microphones described above was optimal for sound pickup from a specific direction. This is because the conventional accessory microphone could not focus its directivity on the beam for the sound pickup target.

Also, it was not always possible to switch the microphone used for a specific application to use it for another application. For example, if a microphone used for a meeting is placed outdoors and used, ambient sound will affect the recording of audio. It wasn't done enough.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and provides a sound pickup device capable of switching the characteristics of a microphone and a microphone so that optimum microphone characteristics can be obtained according to a use environment of the microphone. The purpose is to do. Disclosure of the invention

A sound pickup apparatus according to the present invention for achieving the above object is a sound pickup apparatus that picks up sound by switching the directivity of microphones directed to sound pickup targets located in a plurality of different environments according to the environment. A diaphragm vibrating by a sound pressure; a light source irradiating the diaphragm with a light beam; and a light receiving the reflected light of the light beam irradiated on the diaphragm corresponding to the vibration of the diaphragm. A light detector that outputs a signal; a light source driving circuit that drives the light source to supply a predetermined current; and a negative signal that supplies the signal output from the light detector to the light source driving circuit as a negative feedback signal. An optical microphone including a feedback circuit is used, and a negative feedback amount of the negative feedback circuit is switched according to the environment.

Further, in the sound collection device of the present invention, means for recognizing a voice or noise spectrum from the sound collection target is provided, and an environment in which the sound collection target is located can be determined based on the recognition result.

Further, in the sound pickup device of the present invention, the spectrum can be recognized at an arbitrary time. BRIEF DESCRIPTION OF THE FIGURES

【Figure 1】

FIG. 1 is a configuration diagram illustrating a main configuration of a sound collection device according to the present invention.

【Figure 2】

FIG. 4 is a diagram showing a change in the directivity pattern of the optical microphone element used in the present invention.

[Figure 3]

FIG. 2 is a diagram showing a structure of an optical microphone element used in the present invention. P

Three

[Fig. 4]

The figure which shows the structure of the other optical microphone element used for this invention.

[Figure 5]

FIG. 1 is a circuit diagram illustrating a schematic configuration of an optical microphone device used in the present invention.

[Fig. 6]

FIG. 5 is a change diagram of the directivity pattern of the optical microphone element of FIG.

[Fig.7]

FIG. 4 is a directional pattern diagram of an optical microphone element used in the present invention.

[Fig. 8]

FIG. 9 is a configuration diagram illustrating a main configuration of another embodiment of the present invention.

[Fig. 9]

FIG. 4 is a diagram showing a recognition result of a speech spectrum using the present invention.

[Fig. 10]

The figure which shows the external appearance structure of the sound collection device of this invention. BEST MODE FOR CARRYING OUT THE INVENTION

The sound collecting device of the present invention uses an optical microphone as a microphone for collecting sound.

Prior to describing an embodiment of the sound pickup device of the present invention, the basic principle and configuration of an optical microphone used in the present invention will be described below. FIG. 3 is a diagram showing a structure of a head portion of the optical microphone element 50.

Inside the microphone head 1, a diaphragm 2 that vibrates when hit by a sound wave is stretched, and a surface 2a on the side to which the sound wave hits is exposed to the outside. Accordingly, the sound wave 7 reaches the surface 2a and vibrates the diaphragm 2. A light source 3 such as an LED for irradiating a light beam obliquely to the surface 2 b of the diaphragm 2 is provided inside the head 1 located on the surface 2 b opposite to the surface 2 a of the diaphragm 2. A lens 4 for converting the light beam from 3 into a predetermined beam shape, and receives the reflected light whose beam surface is reflected by surface 2b A light detector 5 and a lens 6 are provided to enlarge the displacement of the optical path of the reflected light due to the vibration of the diaphragm 2.

When the vibration plate 2 vibrates when the sound wave 7 strikes the surface 2a of the vibration plate 2 in this manner, the light receiving position of the reflected light incident on the photodetector 5 on the light receiving surface 5a changes. If the photodetector 5 is configured as a position sensor, an electric signal corresponding to the vibration of the diaphragm 2 is extracted from the position where the reflected light is irradiated. This is the basic structure of an optical microphone. However, the optical microphone shown in Fig. 3 cannot expect much noise reduction.

That is, the diaphragm 2 also vibrates due to the noise reaching the diaphragm 2, and this is superimposed on the vibration by the normal sound wave 7 as a noise signal. An optical microphone having a structure as shown in FIG. 4 has been known as an optical microphone which has reduced the influence of this noise and has further improved the noise reduction effect.

In the structure shown in FIG. 4, the diaphragm 2 vibrating by the sound wave 7 is stretched almost at the center of the head 1. The first opening 15 and the second opening 16 are provided on both sides of the head 1 so as to be symmetrical with respect to the diaphragm 2.

With such a configuration, sound waves enter the head 1 from any of the openings and vibrate the diaphragm 2. In the optical microphone element 50 shown in FIG. 4, when the amplitude and the phase of the sound wave entering from the first opening 15 and the sound wave entering from the second opening 16 are equal, these two sound waves vibrate. The two sides 2a and 2b of the plate 2 do not cancel each other and vibrate the diaphragm 2.

It is known that when two microphone elements having the same receiving sensitivity are arranged close to each other and a sound wave generated at a long distance is received, the two microphone elements detect the incoming sound waves equally.

—In general, sound waves are emitted from the mouth of a person at a short distance from the microphone element That is, sound is generated at a short distance from the microphone element. This short-range person's voice has a spherical field characteristic as shown by the circular curve. On the other hand, sound waves generated at a long distance, for example, by noise and acoustics have the properties of a plane field. The acoustic intensity of a spherical wave is approximately the same along its sphere or envelope and varies along the radius of the sphere, but for a plane wave, the acoustic intensity is approximately the same at all points in the plane. Therefore, the optical microphone element as shown in Fig. 4 can be considered as a combination of two microphone elements. As a result, sound waves having substantially the same amplitude and phase characteristics arrive at the diaphragm 2 and cancel each other out as described above, thereby reducing the effect.

On the other hand, the sound wave from the near field is incident nonuniformly from the first opening 15 or the second opening 16 so that the diaphragm 2 is vibrated, and is taken out from the photodetector 5 as a signal. In this way, an optical microphone element capable of further reducing the influence of noise is obtained with the structure of FIG. FIG. 7 is a diagram showing the directivity pattern of the optical microphone element shown in FIGS.

(A) shows the directivity pattern of the optical microphone element 50 shown in FIG. 3, and is substantially a circle having the maximum sensitivity in the direction perpendicular to the diaphragm 2 toward the opening (left side in the figure). It has a directional pattern of shape.

(B) is the directivity pattern of the optical microphone element 50 shown in FIG. 4 and has an almost 8-shaped directivity pattern having the maximum sensitivity in both directions of the openings 15 and 16. Here, FIGS. The directivity pattern of the optical microphone element 50 shown in FIG. 4 can be changed so as to extend in the axial direction showing the maximum sensitivity as shown in FIG. 2 or FIG. 6, or to narrow down in the direction perpendicular to the axis. In order to change the directivity pattern in this way, a part of the detection output from the photodetector 5 is negatively fed back (negative feedback) to a light source driving circuit that drives the light source 3 using a negative feedback circuit. Just do it. FIG. 5 is a diagram showing a schematic configuration of an optical microphone device using a feedback circuit 100 for changing a beam pattern as shown in FIG. 2 or FIG.

The output from the photodetector 5 is taken out through a filter circuit 8 and amplified by an amplifier 9 to become a microphone output. The filter circuit 8 is used to extract only signal components in a desired frequency range. Here, in the optical microphone device shown in FIG. 5, a predetermined current is supplied to the light source 3 through a negative feedback (NFB) circuit 100 by using a part of the output signal extracted from the photodetector 5. The light source driving circuit 13 that drives the lever 3 is configured to be supplied as a negative feedback signal.

The negative feedback circuit 100 includes a small signal amplifier circuit 10, a filter circuit 11 for extracting only a signal component in a desired frequency range from an output thereof, and a comparator 12. A reference power supply 14 serving as a reference voltage is connected to the non-inverting input terminal of the comparator 12. The signal extracted through the filter circuit 1 1 is supplied to the inverting input terminal of the comparator 1 2

With this configuration, the comparator 12 outputs a lower output level as the output of the filter circuit 11 increases, whereby the light source driving circuit 13 operates to reduce the current supplied to the light source 3.

Here, the small signal amplifier circuit 10 amplifies the signal only when the input signal level is lower than a predetermined level, and does not amplify the signal higher than a certain level. Therefore, when the input signal level is higher than a certain level, the output signal level does not change and the amplification (gain) becomes zero. When the input signal is lower than a predetermined signal level, the signal is amplified so that the lower the signal level, the higher the amplification. Furthermore, the rate of increase of the output signal with respect to the input signal increases as the input signal level decreases. Here, since the output from the photodetector 5 is proportional to the volume of the received wave, the output of the small signal amplifier circuit 10 is amplified and output as the volume becomes smaller.

Since this output is input to the inverting input terminal of the comparator 12 through the filter circuit 11, the output level of the comparator 12 decreases as the volume decreases. As a result, the current supplied to the light source 3 operates so that the light output of the light source 3 decreases as the volume decreases. In other words, the lower the volume, the lower the sensitivity of the microphone. Also, since a signal above a predetermined level is not amplified, the light output is not limited at that signal level. Therefore, the sensitivity of the microphone does not decrease. For sounds that come from the axial direction perpendicular to the diaphragm and that do not cause a decrease in microphone sensitivity, shifting the sound from the axial direction leads to sensitivity along the original directivity pattern curve. Gradually decreases. When the level falls below a certain level, the small-signal amplifier circuit 10 has an amplification factor, and the supply current control of the light source drive circuit 13 works to further lower the sensitivity of the microphone. As a result, in the optical microphone device having the negative feedback circuit 100, the pattern of the directional beam is narrower than the directional pattern of the sensitivity as shown in FIG. 2 or FIG. Figures 2 and 6 show the change in the directivity pattern due to the change in the amount of negative feedback.

(A) shows the directivity pattern when no negative feedback is applied. In this case, the pattern is almost circular. Next, the directivity patterns when negative feedback is applied are shown in (B) and (C).

In the case of (B), the amount of negative feedback is small, and in the case of (C), the amount of negative feedback is large. In this way, by changing the amplification degree of the small signal amplifier circuit 10, the amount of negative feedback is changed to extend the directivity pattern of sensitivity in the axial direction of the maximum sensitivity, or to narrow down in the direction perpendicular to the axis. Can be changed to In this manner, the directional characteristics of the sensitivity of the optical microphone can be changed.

The sound pickup device according to the present invention can change such a directional beam pattern. The directional characteristics of the selected microphone are changed using an optical microphone that can be used. FIG. 1 is a configuration diagram showing a main configuration of a sound collection device according to an embodiment of the present invention. In the present invention, the above-described optical microphone element 50 is used as a sound collecting element. The detection signal from the optical microphone element 50 is taken out via the amplifier 9 and becomes an audio signal. A part of the detection signal extracted from the optical microphone element 50 is transmitted through the switching switch 55 to a negative feedback circuit having a different amount of negative feedback. Negative feedback (negative feedback) is provided to the light source drive circuit 13 that drives the element 50.

Therefore, by switching the contact position of the switching switch 55, a predetermined negative feedback circuit is selected and a different amount of negative feedback is applied to the light source drive circuit 13. Accordingly, the beam pattern indicating the directivity of the sensitivity of the optical microphone element 50 is switched as shown in FIG. 2 or FIG. Therefore, the switching positions A, B, C, and N of the switching switch 55 may be switched so as to have an optimal beam pattern according to the use environment. In the embodiment shown in FIG. 1, the negative feedback amount is the smallest at the switching position A of the switching switch 55 and the beam pattern is almost circular, the beam pattern is medium at the position B, and the beam pattern is the most at the position C. It is set to be thin. At position N, no negative feedback is applied. Therefore, the switching switch 55 is switched according to the environment in which the sound pickup device is used, and the setting is made so that the optimum microphone characteristics can be obtained. That is, when used for a conference in a conference room, switch to position B and narrow the beam pattern to a moderate level. In addition, in the case where the sound is picked up from a distant sound pickup object when used outdoors, the position is switched to the position C so that the beam pattern is most narrowed down so that sound from a distant place can be captured with high sensitivity. FIG. 10 is a diagram showing an external configuration of the sound pickup device of the present invention. As shown in FIG. 10 (A), a back hole 57 for taking in sound from behind the optical microphone element 50 is provided. If an optical microphone element having the structure shown in Fig. 4 is used, ambient noise from a distant place can be accurately suppressed.

Further, as shown in FIG. 10 (B), the switching switch 55 may be provided with a slider 56 for sliding a plurality of positions so as to slide and set the plurality of positions.

In the embodiment shown in FIG. 1, the switching switch 55 is configured to be manually switched, but this switching is not necessarily limited to this. Another embodiment of the present invention shown in FIG. 8 shows a configuration in which the switching of the switching switch 55 is performed automatically.

That is, in the embodiment shown in FIG. 8, a part of the audio output signal is configured to be detected by a single-pass filter 61, a band-pass filter 62, and a high-pass filter 63, respectively, to detect the frequency spectrum. I have.

The detected frequency spectrum is analyzed by the microcomputer 64, the use environment of the microphone is recognized from the state of the frequency spectrum, and the switch 55 is switched to the most suitable position based on the recognition result. I'm trying to do it. In each of the filters 61 to 63, a low-frequency part, a medium-frequency part, and a high-temperature part voice or noise spectrum are extracted and analyzed by the microcomputer 64. FIG. 9 shows frequency characteristics from various environments detected by the microcomputer 64 from the frequency spectrum detected by the filters 61 to 63.

Fig. 9 (a) shows an environment in which the signal strength in the low frequency range is weak, and the signal strength increases as the frequency increases. Figure 9 (b) shows an environment in which the signal strength increases in the mid-tone frequency domain. Fig. 9 (c) shows an environment in which the signal strength is high in the low frequency range and the signal strength is low in the high frequency range. Figure Fig. 9 (d) shows an environment in which the signal strength is almost constant in the low to high frequency range. When such a frequency spectrum is obtained as a detection result of the microcomputer 64, the switching of the switching switch 55 is automatically performed in accordance with the spectrum.

In other words, when the spectrum as shown in Fig. 9 (a) or Fig. 9 (c) is obtained, the position is switched to position C in order to narrow the directional beam to the maximum and increase the sensitivity in the sound pickup direction. If the spectrum shown in Fig. 9 (b) is obtained, position B is selected. If the spectrum shown in Fig. 9 (d) is obtained, position N is selected.

Position N is a position that indicates the normal microphone use condition, and is used especially when it is not necessary to narrow down the directional beam pattern.In this case, the operation of the negative feedback circuit is stopped or the negative feedback circuit is used. There is no configuration. Industrial applicability

As described in detail based on the above embodiments, the sound pickup device of the present invention employs an optical switch using a switching switch for selecting a directional characteristic so as to have an optimum microphone characteristic according to an environment where a sound pickup target is located. Since the microphone is switched, sound pickup with reduced ambient noise is possible.

Such a sound pickup device of the present invention makes it possible to reduce the noise reduction level, which is normally limited to 5 to 8 dB, to 20 dB or more. :

Claims

The scope of the claims

1. In a sound pickup device that switches sound directivity according to the environment and picks up sound, the sound pickup device is directed to sound pickup targets located in a plurality of different environments.

A diaphragm vibrating by sound pressure, a light source for irradiating the diaphragm with a light beam, and a light receiving reflected light of the light beam irradiated on the diaphragm and outputting a signal corresponding to the vibration of the diaphragm A light comprising: a detector; a light source driving circuit that drives the light source to supply a predetermined current; and a negative feedback circuit that supplies the signal output from the photodetector to the light source driving circuit as a negative feedback signal. Using microphone,

A sound pickup device characterized by switching a negative feedback amount of the negative feedback circuit according to the environment.

2. The sound pickup device according to claim 1,

A sound pickup apparatus comprising: means for recognizing a voice or noise spectrum from the sound pickup target; and determining an environment in which the sound pickup target is located based on a recognition result.

3. The sound pickup device according to claim 2,

A sound pickup apparatus characterized in that the spectrum is recognized at an arbitrary time.